Improvement in bit-stocks



NITED STATES A.A'rEN'r @Frio IMPROVEMENT IN BIT-STOCKS.

Specificationjbrming part of Leiters Patent No. 7 3,279, dated January14, 1868.

To all whom it may concern:

Be it known that I, CHARLES H. AMIDoN, of Greenfield, in the county ofFranklin and State of Massachusetts, have invented a new and usefulImprovement in Bit-Stocks; and I do hereby declare the following to be afull, clear, and exact description of the same, ref erence being had tothe accompanying drawings, in which- Figure l is a side view ot' thelower end of the bit-stock. Fig. 2 is a longitudinal section ofthestock, showing thejaws in position,and the screw-nut or thiinble. Fig. 3is a longitudinal section of thejaws. Fig. 4 is an end view of the same.Fig. 5 is a longitudinal section of-thejaws and screw-nut or thimble.

The object of this invention is to produce a bitstock which shallreceive and hold any ordinary bit-shank firml y and rigidly, whatevermay be its taper, and. without any tting .thereof whatever, and preventany accidental withdrawal of said shank from its place and it consists,first, in the construction and use of two jaws, which conform to thetaper of the bit-shank, and are forced equally upon `said shank at bothends by a screw-nnt or other device; second, in the special constructionof the end of the bit-stock, to hold said jaws and retain them always inplace; third, in the 'formation of the groove in the edge of each jaw,so that the shoulders of the bit-shank are inclosed, and the accidentalwithdrawal of the bit prevented; and, fourth, in the application and useof a spring, to prevent cramping of the jaws.

1n order that others may understand the construction and operation of myinvention, I will more particularly describe it.

A is the bit-stock, constructed of metal or other suitable material,having at one end the ordinary swiveled head, and at the other theclamping mechanism which forms the subject of this invention, and whichI will now describe.

That end ot' the bit-stock which receives the shank of the bit I will,for convenience, call the foot B, which is cylindrical, somewhat largerthan the shaft of the stock, and has a male screw-thread cut upon itsouter surface,

as shown in Fig. l.

The slot C is cut vertically through the foot B, from its end, as shownin Fig. 1, and within lt-his slot rest the jaws which seizeand hold`erant, as at a, and is then contracted toward the opening or mouth atthat end, as shown clearlyinFig. 2. This thimble screws on to the footB, and serves to force the jaws G G upon the shank of the bit. Thesejaws are constructed in the'form shown in Fig. 3, and

in thickness they are suitable to iill loosely vthe slot O.

At the lower ends of the jaws G G they are attached to each other by a.slightly curved wire, H, which is rigidly set in one part, and projectsloosely through a corresponding hole in the other part. The upper andlower ends of the jaws are beveled, as at b and c, so that they may beforced toward each other by thc inclined surfaces ot' thethimble F andthe l cavity D, when the said thimble is screwed on to the foot B, asshown in Fig. 2. In those surfaces of the jaws G G which are opposed toeach other I form grooves e e, which, when the jaws are in position,form a recess of square section, as shown in Fig. 4.

This recess is made tapering, as shown in Fig. 2, so as to correspondwith the taper ot' the bit-shank, and is largest just within the outerend, so that the shoulders of the bitshank may be inclosed within thecavity e, and the removal of the bit be prevented, except after relaxingthe pressure of the jaws. As these jaws are loosely connected at thelower ends by the pin H, they may either move apart as on a pivot atthat end, or they may be moved bodily away from each other, so as toaccommodate a bit-shank of any size or taper within the capacity of theimplement. These functions are clearly shown in Figs. 2 and 3.

The operation of this invention is extremely cach other by the outer endof the thimble.

This permits the jaws to conform to the taper ot' the bit-shank, andthereby grasp it rmly Y and closely throughout its length, which couldnot be the case it' thel jaws moved from any iixed point or center. Asthe thimble is forced upon the jaws with power the latter are compressedat their lower ends within the mouth of the cavity D, so that theycannot move laterally to the slightest extent, and the bearing andcompression of the thimbleF and foot B through the screw-threads renderthe outer ends of the jaws equally rigid and immovable, and thebit-shank is held with great rmness and rigidity. The spring E serves toraise the jaws out otthe cavity D, when pressure is relaxed, so thatthey will not be liable to cranip or bind therein.

I am aware of the invention patented to WV. H. Barber, 24th May, 1864,and will designate some of the points of difference which exist betweensaid invention and that presented in this patent:

First, Barbersj aws only touch the bitin front of the shoulders; my jawsgrasp it throughout'the whole length ofthe tapered head, and withoutreference to the inclination `of the sides of said head.

Second, the bit-head enters a solid socket in Barbers stock; my stockhas no socket except that formed by the movable jaws indented on theiredges.

Third, in Barbers stock the head ot' the bit must exactly tit solidsocket, or the jaws may close too far in front, or not at all, over theshoulders. In the rst case the bit would slip forward and would not beheld steadily; in the second case the jaws might fail entirely to holdthe bit.

Neither of. these events can happen with my stock, because any bit-headwhich can be inserted will be firmly grasped and held.

Having described my invention, what I claim as new, and desire to secureby Letters Patent, is- Y l. In combination with the jaws G G, or theirequivalents, constructed to move away from or toward each other in themanner described, so that they may conform to the taper of thebit-shank, the screw-thimble F, or its equivalent,`to force the saidjaws upon said shank, as and for the purpose set forth.

2. Thej aws G G, con structed'with the groove, formed substantially asset forth, so as to iuclose the taper sides and the shoulders oi' theshank, as and for the purpose described.

3. The cavity D, formed with a beveled orifice, as shown, in combinationwith the jaws G G, constructed with correspondingly beveled ends, as andfor the purpose shown and den' scribed.

4. The spring E, located in the cavity D, in combination with the jawslGG, as and for the purpose set forth.

CHARLES H. AMIDON.

Witnesses:

L. J. GUNN, J. O. NEWTON.

